Nowadays, users of home or office printers often work with media of sizes ranging from postcards to wide formats like B-size. These media are also available in different thicknesses. To remain competitive, therefore, manufacturers of printers must design their products to handle a wide range of media of different sizes and thicknesses. In addition, these printers must be able to provide high throughput to meet the needs of the more sophisticated and throughput-oriented users. Hence, these printers would require an efficient media output management system in order to be able to satisfy such user needs. This requirement is especially true for printers meant for use in a multi-user network environment.
A simplified side view of a typical wet printed media output management system 10 in an inkjet printer 11 is shown in FIG. 1. As illustrated, a wet printed medium 12 travels over a media support surface, or platen 13, during wet printing in the direction as shown by an arrow A. An ejection mechanism comprising a series of starwheels 14 working together, or cooperating, with a series of output rollers 15 is used to handle the wet printed medium 12 together with a drive mechanism. The drive mechanism is made up of a series of outpinch rollers 16 cooperating with a series of drive rollers 18.
The ejection mechanism performs two essential functions. Firstly, the ejection mechanism pulls on and ejects the wet printed medium 12 once the rear edge of the wet printed medium 12 leaves the outpinch rollers 16. This pulling action is provided by the rotating output rollers 15 which are in frictional contact with the wet printed medium 12. The starwheels 14, in pushing the wet printed medium 12 against the output rollers 15 to provide such a frictional contact, lightly bite into the surface of the wet printed medium 12. The ejection mechanism subsequently ejects and thereby stacks the wet printed medium 12 in an output tray 17. Up until the point when the rear edge of the wet printed medium 12 leaves the outpinch rollers 16, the wet printed medium 12 is carried forward, or caused to advance, over the platen 13 by both the ejection mechanism and the drive mechanism.
Secondly, the ejection mechanism cooperates with the drive mechanism to form a tension, or stretching force, on a portion of the wet printed medium 12 to cause that portion to flatten out. The flatness of the portion of the wet printed medium 12 in turn has an effect on the space between its surface and a pen nozzle 19 which provides the wet print markings, thus affecting the print quality of the wet print markings.
Variations to the typical wet printed media output management system described in the foregoing have been proposed for various reasons. For example, in order to avoid smearing the wet print markings of any previously prepared printed medium, the wet printed medium 12 has to be held for some time before it is placed in the output tray 17. By isolating the wet printed medium 12 from a printed media stack in the output tray 17, or holding the wet printed medium 12, more time is allocated to the wet print markings to dry. This holding time is achieved by forcing the wet printed medium 12 to travel a longer distance, known as holding distance, before it can be placed in the output tray 17. Thus, a series of spaced-apart holding members, or "ramps" 20, are used to hold the printed medium 12 for a predetermined holding distance, as shown in FIG. 2. For such an arrangement, ramp parameters such as the ramp angle and the ramp length are important. In general, steeper and longer ramps 20 will provide an improved holding time.
While such wet printed media output management systems have achieved commercial implementation, they suffer from disadvantages. A disadvantage addressed by the present invention is that with the improved holding time, the resistance provided by the ramps 20 against the advancing wet printed medium 12 also inadvertently increases. Generally, if an increase in the throughput of the inkjet printer 11 is desired, a corresponding longer holding time is required. This longer holding time is necessary because the speed with which the wet printed medium 12 is ejected is high, and therefore the possibility of smearing also increases. However, increasing the angles and lengths of the ramps 20 increases not only the holding time, but also the resistance presented by the ramp 20 against the advancing wet printed medium 12. This ramp resistance commonly exists in two different operations that are part of the printing cycle. During a printing operation which is one of the operations, the ejection mechanism cooperates with the drive mechanism to advance the wet printed medium 12 over the platen 13 and cause a portion of the wet printed medium 12 to flatten out during printing. Therefore, the combined force provided by the cooperating mechanisms in advancing the wet printed medium 12 overcomes the ramp resistance experienced by the wet printed medium 12 during this operation. In contrast, the ramp resistance experienced during an ejection operation, the other operation in the printing cycle in which the ejection mechanism ejects the wet printed medium 12, is overcome solely by the force provided by the ejection mechanism. As a prerequisite therefore, the starwheels 14 need to be activated by larger spring forces. Such larger spring forces will, however, cause the starwheels 14 to leave visible bite marks on the wet printed medium 12. In the instance of a user who is preparing presentation slides using the inkjet printer 11 employing the starwheels 14 activated by such larger spring forces, such bite marks are unacceptable.
The presence of steeper and longer ramps 20 in the inkjet printer 11 also increases the undesirable bending of thick media like postcards, envelopes, Norman media or photography media. In order to overcome this bending problem, the ramps 20 are usually designed to be adjustable to a flat, or horizontal, position by a manually operated lever (not shown). This arrangement is quite useful in alleviating the bending problem when the inkjet printer 11 is used as a standalone printer. However, in a multi-user network environment where many users usually share the inkjet printer 11, the same arrangement may not be feasible at all. In such a situation, additional coordination will be required to manually adjust the ramps 20 to the correct positions for printing on different types of media.
Accordingly, it is an object of the present invention to provide a system for managing wet printed media output in a printing device capable of handling multiple media sizes and thicknesses in a multi-user network environment.